Motor driven blower unit



- Aug. 8, 1933. J. M. CANTWELL MOTOR DRIVEN BLOWER UNIT Filed April 25,1927 M INVENTOR.

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Patented Aug. 8, 1933 MOTOR DRIVEN BLOWER UNIT Joseph M. Cantwell,Albany, N. Y.

Application April 25, 1927.

1 Claim.

The present invention relates to blowers, and particularly to devices ofthis character adapted for creating a forced draft in furnaces or thelike. and for general use where it is desirable to deliver acomparatively large volume of air in a highly diffused state atcomparatively low pressure.

Where blowers of the present type are used for plying air to the plenumchamber of a furve or the ke, it is practically impossible to maintain au; form rate of combustion over the entire grate area. These blowersmerely create a unidirectional movement of a column of air which, whenit enters the plenum chamber, ap-

parently does not create or maintain therein a amount of air, and thuseffect an ever increas ing variation in the rate of combustion in thedifiercnt zones of the furnace.

With these disadvantages of the present blowers in mind, the primaryobject of my invention is to provide a device of this character whichwill deliver a large volume of air in such a way that, after leaving thedraft tube of the blower, it will become rapidly diffused and intermixedwith the surrounding air. Another objectis to provide a blower whichwill deliver a large volume of air to the plenum chamber of a furnace orthe like, and in such a way that the development of hot spots in thefuel bed will be substantially prevented. Another object is to provide ablower which will deliver a greater volume of air with less power inputthan is possible with blowers of the present type. A further object isto provide, in connection with a blower of this general character, anautomatically operated check damper which will prevent the back-flow ofair through the draft tube when the blower is not in operation.

With these objects in view, my invention includes the novel elements,and the combinations and arrangements of elements described below andillustrated in the accompanying drawing, in which Fig. 1 is a verticalsectional view through the blower with the motor in elevation;

Fig. 2 is a sectional view on line 22 of Fig. 1; and

Serial No. 186,287

Fig. 3 isa view. of the fan.

Referring to the drawing, 10 indicates a caswhich may be constructed inany suitable manner to provide merely a carrier for the fan, ll, or toalso provide asupport for a motor, 12, and a draft tube for the blower,as shown. In the embodiment illustrated, an electric motor, 12, isbolted or otherwise secured to the intake end of the casing so that itsshaft is substantially coaxial with the axis of the tube, and afan, 1].,pinned or keyed directly to the motor shaft. The blades of the fan, 11,are preferably, though not necessarily, of the type shown and terminatein close proximity to the wall of the casing.

Within the casing and on the discharge side of the fan, or, in otherwords, Within What is ordinarily termed the draft tube, are a pluralityof separate elements, 13, which are designed to give a whirling motionto the column of air impelled by the fan. These elements are carried bythe casin and preferably may be cast as an integral part thereof. Theymight, perhaps, be described as fin-like projections which extendinwardly only a comparatively short distance from the inner periphery ofthe casing, so that the central portion of the draft tube isunobstructed, and are downwardly inclined or pitched in the direction ofrotation of the fan to provide guides for changing the otherwise normalaxial movement of the air column to a spiral or whirling movement. Theprovision of the fins or blades makes the entire area of the blades ofthe propeller and the blower more effective. The surfaces of theseelements against which the air impingesmay be plane, helicoidal orotherwise so long as they are adapted to impart a whirling motion to theair, and generally of any pitch desired, although too fiat a pitch willcause a slight puff back through the intake at high fan speeds and is,therefore, not desirable.

It is well known that the fan, in addition to producing a forward ordriving movement of the air, also produces a whirling movement. Byplacing the fins in the draft tube or casing at the points illustratedin the drawing, that is, with theirupper ends just below the fan, andextending them only a short distance (measured axially of the tube),they intercept or pick off the air as it leaves the fan and modify thedirect forward movement thereof by imparting a decided whirling movementto the air column, thus augmenting the whirling movement established bythe fan. This whirling movement, densifies the air in the outer part ofthe column and rarefies the air in the center so that a marked increasein the efiiciency of the blower is noted. When the whirling column ofair passes the discharge opening in the draft tube and is no longerlaterally confined, it becomes highly diffused, spreading out in alldirections and thus rapidly intermixing with the air into which it isprojected.

In order to protect both the fan and the motor from the detrimentaleffect of dust or other foreign matter from the ash pit, which usuallycirculates incident to the opening of the door of the ash pit, I haveprovided an automatically operable damper, 14, arranged within the drafttube or casing, 10, so that access may be had to the ash pit withoutsubjecting the fan or motor to the effect of dust. This damper ispivoted off center, as at 15, and carries a counter weight.- 16, so thatit will automatically gravitate to its normal closed position when themotor, 12, is stopped and the current of air through the casing ceases.The damper should fit rather loosely at the sides near the ends of thepivotal axis and this axis should be quite close to the center of thedamper, as shown. When the blower is in use, the current of air passingthrough the casing is utilized to maintain the damper, 14, fully opened,but when it is desired to open the door of the ash pit, the motor isfirst stopped, thereby allowing the damper to automatically gravitate toa closed position for the purpose stated.

While I have described my invention in its preferred embodiment it is tobe understood that the Words which I have used are words of descriptionrather than of limitation and that changes within the purview of theappended claim may be made Without departing from the true scope andspirit of my invention in its broadest aspects.

What I claim is-- In a blower, including a rotating fan of the propellertype, a tubular member through which the air is impelled by the fancharacterized by having a plurality of stationary projecting elementsinclined to the axis of said member and disposed about the inner surfacethereof from JOSEPH M. CANTWELL.

